Photonic topological fermi nodal disk in non-Hermitian magnetic plasma.

Topological physics mainly arises as a necessary link between properties of the bulk and the appearance of surface states, and has led to successful discoveries of novel topological surface states in Chern insulators, topological insulators, and topological Fermi arcs in Weyl, Dirac, and Nodal line semimetals owing to their nontrivial bulk topology. In particular, topological phases in non-Hermitian systems have attracted growing interests in recent years. In this work, we predict the emergence of the topologically stable nodal disks where the real part of the eigen frequency is degenerate between two bands in non-ideal magnetohydrodynamics plasma with collision and viscosity dissipations. Each nodal disk possesses continuously distributed topological surface charge density that integrates to unity. It is found that the lossy Fermi arcs at the interface connect to the middle of the projection of the nodal disks. We further show that the emergence, coalescence, and annihilation of the nodal disks can be controlled by plasma parameters and dissipation terms. Our findings contribute to understanding of the linear theory of bulk and surface wave dispersions of non-ideal warm magnetic plasmas from the perspective of topological physics. Scientists have applied a modern theory to gain further insight into the century-long study of warm plasma, a product of nuclear fission reactions. ‘Topological band theory’ was recently developed to describe electron energies in a type of material that is insulating on its inside and conducting on its surface. Shuang Zhang of the University of Birmingham, UK, and colleagues applied the theory to further understand electromagnetic wave dynamics in warm plasma, a gas consisting of freely moving ions, nuclei and electrons. The team’s equations incorporated information on dissipations from particle collisions and viscosity forces, allowing them to predict some of the nontrivial topological behaviors within warm plasma. Their work is of benefit to fundamental science and to improving understandings of the solar corona, synchrotron radiation, and the production of energy from controlled thermonuclear reactions.